Liquid leakage prevention device, liquid leakage prevention method, and liquid cooling system

ABSTRACT

In a liquid cooling system having a structure in which a joint is attached or detached while inserting or removing a card board, when a liquid is leaked from a connection portion of the joint, the leaked liquid confined within a housing is prevented from spilling out and scattering to surrounding electronic components when the card board is disconnected. The liquid cooling system includes male and female joints, and housings that fix those joints to each other. A water absorptive material is disposed on an inner wall of the housing of the male joint, and a seal member is disposed on an inner wall of the housing of the female joint. The liquid cooling system includes a liquid leakage detection function. When the liquid cooling system detects the liquid leakage, the liquid cooling system stops the operation of a pump, and prevents the liquid from being further leaked.

CLAIM OF PRIORITY

The present application claims priority from Japanese patent application JP 2012-095291 filed on Apr. 19, 2012, the content of which is hereby incorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a liquid leakage prevention device, a liquid leakage prevention method, and a liquid cooling system, and more particularly to a liquid leakage prevention device, a liquid leakage prevention method, and a liquid cooling system for use in an electronic device, having a liquid leakage prevention structure of a pipe joint, and a liquid leakage prevention structure of the pipe joint.

2. Background Art

A semiconductor component used for the electronic device produces heat during operation. There is a need to cool the semiconductor component because the semiconductor component loses a function of semiconductor when the semiconductor component exceeds a given temperature. As a method of cooling the semiconductor component, an air cooling method is frequently applied. However, in recent years, higher integration of the semiconductor component is advanced, and a liquid cooling method high in cooling efficiency is being spread with an increase in the heat generation density.

FIG. 2 is a conceptual diagram illustrating a configuration of a general liquid cooling system.

A basic configuration of the liquid cooling system will be described with reference to FIG. 2. The liquid cooling system includes a pump 101, a heat radiation unit 104, a reserve tank 102, and a heating receiving jacket 103, and a metal pipe or a rubber tube is plumbed between the respective units. A piping 105 is filled with a refrigerant liquid, and the refrigerant liquid is circulated by the pump 101 to transform the heat. In FIG. 2, the heat generated from a heater element such as the semiconductor component is propagated to the refrigerant liquid through the heating receiving jacket 103, and transported to a radiator. The heat radiation unit 104 includes a radiator, and a cooling fan, and is of a mechanism in which the refrigerant liquid within the radiator is cooled by air cool. The reserve tank 102 reserves the cooling liquid, and keeps a constant output.

Incidentally, in a computer device field, there is used an electronic device that realizes a plurality of functions by inserting plural types of cardboards into one housing. An example using the liquid cooling method in the electronic device of this type is disclosed in JP-A-2009-15869.

FIG. 3 is a conceptual diagram illustrating an example of a liquid cooling system in the related art.

Hereinafter, a configuration example of JP-A-2009-15869 will be described with reference to FIG. 3. A plurality of card boards 9 on which electronic components are mounted are loaded within a housing, and are connected to one backplane 8 by electric connectors. Also, a plurality of heater elements mounted on each of the cardboards 9 are connected to one heating receiving jacket 103. Further, the heating receiving jacket 103 is plumbed to the pump 101 for circulating the refrigerant liquid and the heat radiation unit 104 (radiator, fan) through joints, and a heat from the heater elements can be transported and radiated to an external air. According to this device configuration, when a failure occurs in a part of components mounted thereon, or the system is abnormal, only the cardboard 9 in question is extracted and maintained to enable service provision without stopping the overall system.

SUMMARY OF THE INVENTION

Because the joints used in JP-A-2009-15869 require a liquid leakage prevention property at the time of attachment or detachment, the joints are structured as follows. The valves are provided for both of a male side and a female side inside of the joint, and when the joints are not connected, the valves are closed. On the other hand, when those valves are connected, both of the valves are opened to circulate the refrigerant liquid.

However, in the related art joint as disclosed in JP-A-2009-15869, for example, when the cardboard is attached or detached at the time of operating the system, it is assumed that the internal refrigerant liquid cannot be surely prevented from being leaked to the external by the attachment or detachment work. Also, there is a possibility that a liquid is leaked from a connection portion of the joint, and affects the reliability of an electronic device, for example, when a foreign matter such as dust is caught by the joint at the time of attaching or detaching the joint, or when a rubber ring for tightly sealing a liquid is damaged or deteriorated.

Under the circumstances, solutions to the above problems will be described below.

FIG. 4 is a cross-sectional view illustrating a liquid leakage prevention structure of a joint, which is a cross-sectional view illustrating a state before a male joint and a female joint are fitted to each other. In this example, the mail joint and the female joint are fixed to respective housings, and those housings have a lock mechanism (not shown) for holding a state in which those joints are fitted to each other. Also, those housings are shaped so that the connection portion is sealed by the housings when the joints are fitted to each other. Further, a seal material such as a rubber packing is provided on a housing inner wall of the female joint.

FIG. 5 is a cross-sectional view illustrating the liquid leakage prevention structure of the joint, which is a cross-sectional view illustrating a state in which the male joint and the female joint have been fitted to each other. When the joints are fitted to each other, the seal member attached to the housing inner wall of the female joint is pressed by the housing of the male joint to seal a space within the housing. Also, in this situation, a lock mechanism (not shown) of the housing operates to hold the fitting state, and therefore even if a liquid is leaked from the connection portion, the liquid can be prevented from being leaked out of the housing.

Even with the liquid leakage structure of the joint in FIGS. 4 and 5, as described above, there is the possibility that the liquid is leaked from the connection portion of the joint, and affects the reliability of an electronic device, for example, when the foreign matter such as dust is caught by the joint at the time of attaching or detaching the joint, or when the rubber ring for tightly sealing the liquid is damaged or deteriorated.

FIG. 6 is a cross-sectional view illustrating the liquid leakage prevention structure of the joint, which illustrates a state in which the male joint and the female joint are disconnected from each other after the liquid has been leaked from the connection portion of the joint at the time of fitting.

Joints 1 and 2 are of a structure in which the liquid is shut within housings 3 and 4 if the liquid is leaked. For that reason, when the male joint 1 is removed from this state, as illustrated in FIG. 6, there is a possibility that the liquid shut within the housings 3 and 4 runs over (is leaked), and scatters to the surrounding electronic components.

The invention has been made in view of the above circumstances, and an object of the invention is to provide a structure in which safe insertion and removal of cardboards are enabled without leaking the liquid to the external even if a liquid is leaked from a connection portion of joints, in a liquid cooling system having a structure in which joints for refrigerant liquid are attached or detached while the card boards are inserted or removed.

The joint according to the invention includes, for example, a male joint and a female joint, and housings for fixing those joints together. When the joints are not connected to each other, the male joint and the female joint close flow channels. On the other hand, when those joints are connected to each other, the flow channels of those joints are opened so that the refrigerant liquid can flow thereinto. Also, the housings can be shaped so that a seam portion is sealed by the housings when the joints are fitted to each other. Further, a water absorptive polymer is disposed on a housing inner wall of the male joint, and a seal member is disposed on a housing inner wall of the female joint.

Also, the liquid cooling system may have a function of detecting the liquid leakage. Further, when the liquid leakage is detected, the operation of a pump stops so that the liquid can be prevented from being further leaked.

According to the first solving means of the present invention, there is provided a liquid leakage prevention device in a liquid cooling system, comprising:

a first joint of a liquid connector which connects a pipe for allowing a refrigerant liquid to flow to a heat receiving jacket for cooling an electronic component mounted on a board;

a second joint of the liquid connector which is fitted to the first joint;

a first housing that fixes the first joint to an interior thereof;

a second housing that is fitted to the first housing from an exterior, and fixes the second joint to an interior thereof;

a seal member that is disposed on an inner wall of the second housing, and confines the refrigerant liquid leaked from a connection portion of the first joint and the second joint within a space formed when the first housing and the second housing are fitted to each other; and

a water absorptive material that is disposed on an inner wall of the first housing, and absorbs the refrigerant liquid confined within the space.

According to the second solving means of the present invention, there is provided a liquid leakage prevention method in a liquid cooling system, comprising:

connecting a pipe for allowing a refrigerant liquid to flow to a heat receiving jacket for cooling an electronic component mounted on a board by a first joint of a liquid connector;

fitting a second joint of the liquid connector to the first joint;

internally fixing the first joint by a first housing;

fitting a second housing to the first housing from an exterior, and fixing the second joint to an interior thereof;

confining, by a sealing member disposed on an inner wall of the second housing, the refrigerant liquid leaked from a connection portion of the first joint and the second joint within a space formed when the first housing and the second housing are fitted to each other; and

absorbing the refrigerant liquid confined within the space by a water absorptive material that is disposed on an inner wall of the first housing.

According to the third solving means of the present invention, there is provided a liquid cooling system, comprising:

a board on which an electronic component is mounted, which is inserted into a backplane or removed from the backplane;

a heat receiving jacket that covers the electronic component, and internally circulates a refrigerant liquid to cool the electronic component at the time of inserting the board into the backplane;

a pump that circulates the refrigerant liquid;

a reserve tank that reserves the refrigerant liquid;

a heat radiation unit that cools the refrigerant liquid; and

a liquid leakage prevention device of a refrigerant liquid,

wherein

the liquid leakage prevention device, comprising:

a first joint of a liquid connector which connects a pipe for allowing a refrigerant liquid to flow to a heat receiving jacket for cooling an electronic component mounted on a board;

a second joint of the liquid connector which is fitted to the first joint;

a first housing that fixes the first joint to an interior thereof;

a second housing that is fitted to the first housing from an exterior, and fixes the second joint to an interior thereof;

a seal member that is disposed on an inner wall of the second housing, and confines the refrigerant liquid leaked from a connection portion of the first joint and the second joint within a space formed when the first housing and the second housing are fitted to each other; and

a water absorptive material that is disposed on an inner wall of the first housing, and absorbs the refrigerant liquid confined within the space,

wherein

the board is connected to the backplane by an electric connector, and the heat receiving jacket on the substrate is connected to the backplane by the liquid connector having the first and second joints, and

the pump circulates the refrigerant liquid in a path including the reserve tank, the liquid connector having the first and second joints, the heat receiving jacket, and the heat radiation unit, to cool the refrigerant liquid.

According to the fourth solving means of the present invention, there is provided a liquid cooling system, comprising:

a board on which an electronic component is mounted, which is inserted into a backplane or removed from the backplane;

a heat receiving jacket that covers the electronic component, and internally circulates a refrigerant liquid to cool the electronic component at the time of inserting the board into the backplane;

a pump that circulates the refrigerant liquid;

a reserve tank that reserves the refrigerant liquid;

a heat radiation unit that cools the refrigerant liquid; and

a liquid leakage prevention device of a refrigerant liquid,

first and second flow rate sensors that are disposed on an inflow side and an outflow side of the reserve tank;

a detection unit that detects the liquid leakage by monitoring a difference between the first and second flow rate sensors,

wherein

the liquid leakage prevention device comprising:

a first joint of a liquid connector which connects a pipe for allowing a refrigerant liquid to flow to a heat receiving jacket for cooling an electronic component mounted on a board;

a second joint of the liquid connector which is fitted to the first joint; a first housing that fixes the first joint to an interior thereof;

a second housing that is fitted to the first housing from an exterior, and fixes the second joint to an interior thereof;

a seal member that is disposed on an inner wall of the second housing, and confines the refrigerant liquid leaked from a connection portion of the first joint and the second joint within a space formed when the first housing and the second housing are fitted to each other; and

a water absorptive material that is disposed on an inner wall of the first housing, and absorbs the refrigerant liquid confined within the space,

wherein

the board is connected to the backplane by an electric connector, and the heat receiving jacket on the substrate is connected to the backplane by the liquid connector having the first and second joints, and

the pump circulates the refrigerant liquid in a path including the reserve tank, the liquid connector having the first and second joints, the heat receiving jacket, and the heat radiation unit, to cool the refrigerant liquid.

According to the present invention, it is possible to provide a structure in which safe insertion and removal of card boards are enabled without leaking the liquid to the external even if a liquid is leaked from a connection portion of joints, in a liquid cooling system having a structure in which joints for refrigerant liquid are attached or detached while the card boards are inserted or removed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating a structure of a joint according to a first embodiment of the invention, which illustrates a state before a male joint and a female joint are fitted to each other;

FIG. 2 is a conceptual diagram illustrating a configuration of a general liquid cooling system;

FIG. 3 is a conceptual diagram illustrating an example of a liquid cooling system in a related art;

FIG. 4 is a cross-sectional view illustrating a liquid leakage prevention structure of a joint, which illustrates a state before a male joint and a female joint are fitted to each other;

FIG. 5 is a cross-sectional view illustrating the liquid leakage prevention structure of the joint, which illustrates a state in which the male joint and the female joint have been fitted to each other;

FIG. 6 is a cross-sectional view illustrating the liquid leakage prevention structure of the joint, which illustrates a state in which the male joint and the female joint are disconnected from each other after the liquid has been leaked from the connection portion of the joint at the time of fitting;

FIG. 7 is a perspective view illustrating a structure of the joint according to the first embodiment of the invention, which illustrates a method of fixing a water absorptive polymer to a housing;

FIG. 8 is a cross-sectional view illustrating the structure of the joint according to the first embodiment of the invention, which illustrates a state in which the male joint and the female joint have been fitted to each other;

FIG. 9 is a conceptual diagram illustrating a configuration of a liquid cooling system according to this embodiment;

FIG. 10 is a cross-sectional view illustrating the structure of the joint according to the first embodiment of the invention, which illustrates a behavior at the time of leaking the liquid;

FIG. 11 is a cross-sectional view illustrating a structure of a joint according to a second embodiment of the invention;

FIG. 12 is a cross-sectional view illustrating a behavior at the time of leaking the liquid in the joint according to the second embodiment of the invention;

FIG. 13 is a cross-sectional view illustrating a modified example of the structure of the joint according to the second embodiment of the invention; and

FIG. 14 is a cross-sectional view illustrating a structure of a joint according to a third embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the invention will be described with reference to the accompanying drawings.

A. Liquid Leakage Prevention Device (Joint Structure) First Embodiment

FIG. 1 is a cross-sectional view illustrating a structure of a joint according to a first embodiment of the invention, which illustrates a state before a male joint 1 and a female joint 2 are fitted to each other. The joint according to this embodiment includes the male joint 1 and the female joint 2, and housings 3 and 4 that fix those joints to each other. Those housings 3 and 4 include a lock mechanism (not shown) for holding a state where the male joint 1 and the female joint 2 are fixed to each other. A water absorptive material 5 such as a water absorptive polymer is disposed on an inner wall of the housing 3 of the male joint 1, and a seal member 6 such as a rubber packing is disposed on an inner wall of the housing 4 of the female joint 2. In this example, the water absorptive material 5 (water absorptive polymer, etc.) is made of, for example, a material processed into a sheet shape, and has a size or volume as large as at least a liquid having the same volume as that of a space sealed by the housings 3 and 4 can be absorbed. Further, a surface on which the water absorptive material 5 (water absorptive polymer, etc.) is placed may be fitted to all of surfaces that cover the inner walls of the housings 3 and 4, may be fitted to a surface (for example, a lower plane in a direction of gravitational force) on which the refrigerant liquid is liable to be reserved, or may be fitted to an appropriate position on that surface and lateral surfaces. When a liquid other than water is used as the refrigerant liquid, the water absorptive material is not limited to the water absorptive polymer, but a material that can absorb the liquid can be appropriately used.

Also, as a method of fixing the water absorptive material 5 (water absorptive polymer, etc.), the water absorptive material 5 may be attached to an inner wall of the housing 3 of the male joint 1 by using an adhesive so that the water absorptive material 5 does not easily drop off due to attachment or detachment of the joint.

FIG. 7 is a perspective view illustrating a structure of the joint according to the first embodiment of the invention.

As a method of fixing the water absorptive material 5 (water absorptive polymer, etc.) to the housing, as illustrated in FIG. 7, a protrusion 71 may provided on the water absorptive material 5 (water absorptive polymer, etc.), and a groove 72 that fixes the protrusion 71 may be formed in the inner wall of the housing 3.

FIG. 8 is a cross-sectional view illustrating the structure of the joint according to the first embodiment of the invention, which illustrates a state in which the male joint and the female joint have been fitted to each other.

Subsequently, the state in which the male joint 1 and the female joint 2 are fitted to each other will be described with reference to FIG. 8.

When the male joint 1 and the female joint 2 are fitted to each other, the seal member 6 attached to the inner wall of the housing 4 of the female joint 2 is pressed by the housing 3 of the male joint 1, to thereby ensure a sealing property of the space within the housing 4. Also, in this situation, the lock mechanism (not shown) of the housing 4 operates to hold the fitting state, as a result of which even if the liquid is leaked from the seam, the liquid can be prevented from being leaked to the external of the housing 4.

Hereinafter, a description will be given of the behavior when the liquid is leaked from the connection portion at the time of fitting the joints together in the configuration of the first embodiment.

FIG. 10 is a cross-sectional view illustrating the structure of the joint according to the first embodiment of the invention, which illustrates the behavior at the time of leaking the liquid.

As illustrated in FIG. 10, when the liquid is leaked from the connection portion at the time of fitting the joints to each other, a leaked water is confined in the sealed space within the housings 3 and 4. Because all of the liquid confined within the housings 3 and 4 are absorbed by the water absorptive material 5 (water absorptive polymer, etc.), no liquid is present within the housings 3 and 4. For that reason, even if the male joint 1 is disconnected from this state, there is no concern that the refrigerant liquid is scattered to the surrounding electronic components, and the safe insertion and removal of the card boards 9 are enabled.

The male joint 1 of the card boards 9 side and the female joint 2 on the backplane 8 side may be arranged reversely. Also, the housing 3 on the card boards 9 side and the housing 4 on the backplane 8 side may be arranged reversely.

B. Liquid Leakage Detection

Hereinafter, a description will be given of the liquid cooling system for detecting the liquid leakage and the liquid leakage prevention device (joint device) used in the liquid cooling system.

(1) Liquid Cooling System

FIG. 9 is a conceptual diagram illustrating a configuration of the liquid cooling system according to this embodiment. In this embodiment, as compared with the liquid cooling system in FIG. 2, flow rate sensors S1 and S2 are added to an inflow side and an outflow side of the reserve tank 102, and a detector circuit 91 is provided. Referring to FIG. 9, the same symbols as those in FIG. 2 denote the identical configurations. There are kinds of an ultrasonic type and a differential pressure type as the flow rate sensors S1 and S2. In this example, any type is applicable. In this system, if no liquid leakage occurs, because the flow rate of the overall system is always held constant, a relationship between a flow rate Qin on the inflow side and a flow rate Qout on the outflow side satisfies Qin=Qout. On the other hand, if the liquid is leaked in a flow channel flowing from the flow rate sensor S2 to the flow rate sensor S1 through the heating receiving jacket 103, the amount of refrigerant liquid flowing in this flow channel is decreased, resulting in a reduction of the flow rate Qin. However, the flow rate Qout is not changed because the refrigerant liquid is replenished in the reserve tank 102. That is, if the liquid leakage occurs, a relationship of Qout>Qin is satisfied. Because of this principle, the flow rate sensors S1 and S2 are provided on the inflow side and the outflow side of the reserve tank 102, respectively, and the detector circuit 91 monitors a difference between the flow rate sensors S1 and S2 to enable detection of the liquid leakage.

In this embodiment, if the liquid is leaked from the connection portion at the time of fitting the joints together, the leaked water is confined in the sealed space within the housings 3 and 4. In this situation, as described with reference to FIG. 9, when the liquid leakage is detected due to a liquid leakage detection function that the detector circuit 91 compares the flow rates of the flow rate sensors S1 and S2 with each other, the operation of the pump 101 is set to stop. With this setting, the liquid can be prevented from being further leaked from the joint connection portion.

(2) Liquid Leakage Prevention Device (Joint Device) Second Embodiment

FIG. 11 is a cross-sectional view illustrating a structure of a joint according to a second embodiment of the invention.

Incidentally, as another means for detecting the liquid leakage, there is proposed a method stated below.

Referring to FIG. 11, a depression is formed in the inner wall of the housing 3 of the male joint 1, and a pressure sensor 111 is provided within the depression. The pressure sensor 111 is connected to a liquid leakage detector circuit 113 mounted on the card board 9 by a cable 112 passing through the housing 3, and monitors a pressure value applied to the pressure sensor 111. Also, a water swellable water stop material that can absorb at least a liquid of the same volume as that of the space confined in the housing 3 is installed on the inner wall of the housing 3 as the water absorptive material 5.

FIG. 12 is a cross-sectional view illustrating a behavior at the time of leaking the liquid in the joint structure according to the second embodiment. In this example, if the liquid is leaked, the liquid is absorbed by the water absorptive material 5 (water swellable water stop material) provided on the inner walls of the housings 3 and 4. In this situation, when the water absorptive material 5 (water swellable water stop material) is swelled and comes in contact with the pressure sensor 111, a pressure value is changed to quickly detect the liquid leakage within the housings 3 and 4. In this situation, as in the first embodiment, the operation of the pump 101 is set to stop, to thereby enable the liquid to be prevented from being further leaked from the joint connection portion. It is desirable to use the water swellable water stop material larger in volume expansion coefficient so that the pressure sensor 111 and the water absorptive material 5 (water swellable water stop material) surely come in contact with each other even if the amount of liquid leakage is small. Further, an installation position of the pressure sensor 111 is set to a place where the refrigerant liquid is liable to be reserved (for example, beneath the joint connection portion in the direction of gravitational force), thereby making it easy to quickly detect the liquid leakage.

FIG. 13 is a cross-sectional view illustrating a modified example of the structure of the joint according to the second embodiment of the invention.

Also, as in this modified example, in the second embodiment, a switch 131 such as a button switch may be installed instead of the pressure sensor 111 so that the water swellable water stop material is swelled to push the switch 131, and the liquid leakage is detected by the liquid leakage detector circuit 113.

Further, referring to FIGS. 11 and 13, the liquid leakage detector circuit 113 is set to stop the operation of the pump 101 at the time of detecting the liquid leakage, thereby being capable of preventing the liquid from being further leaked from the joint connection portion.

The male joint 1 on the card boards 9 side and the female joint 2 on the backplane 8 side may be arranged reversely. Also, the housing 3 on the card boards 9 side and the housing 4 on the backplane 8 side may be arranged reversely. In this case, the liquid leakage detector circuit 113 can be located on the backplane 8 side.

Third Embodiment

FIG. 14 is a cross-sectional view illustrating a structure of a joint according to a third embodiment of the invention.

Further, as another means for detecting the liquid leakage, a liquid leakage sensor 141 shown in the figure may be used. Referring to FIG. 14, the water absorptive material 5 (water absorptive polymer, etc.) is disposed on the inner wall of the housing 3 of the male joint 1, and the liquid leakage sensor 141 is installed on the water absorptive material 5 (water absorptive polymer, etc.). There are several types of liquid leakage sensors 141, and as the most general type, for example, paper is wrapped around each of two conductive wires, and the two conductive wires are bundled together, and installed in a place where the liquid leakage is sensed. If the liquid is leaked, water penetrated into paper reduces an electric resistance between the two conductive wires, and the reduction of the electric resistance is electrically sensed to output an alarm. If non-conductive liquid is used as the refrigerant liquid, the liquid leakage sensor 141 of an optical type may be used.

The liquid leakage sensor 141 of this type is installed within each of the housings 3 and 4, and connected to a liquid leakage detector circuit 142 mounted on the card board 9 by a cable, thereby being capable of quickly detecting the liquid leakage.

Also, as in the second embodiment, the liquid leakage detector circuit 142 is set to stop the operation of the pump 101 at the time of detecting the liquid leakage, thereby being capable of preventing the liquid from being further leaked from the joint connection portion.

The male joint 1 on the card boards 9 side and the female joint 2 on the backplane 8 side may be arranged reversely. Also, the housing 3 on the card boards 9 side and the housing 4 on the backplane 8 side may be arranged reversely. In this case, the liquid leakage detector circuit 142 can be provided on the backplane 8 side. 

1. A liquid leakage prevention device in a liquid cooling system, comprising: a first joint of a liquid connector which connects a pipe for allowing a refrigerant liquid to flow to a heat receiving jacket for cooling an electronic component mounted on a board; a second joint of the liquid connector which is fitted to the first joint; a first housing that fixes the first joint to an interior thereof; a second housing that is fitted to the first housing from an exterior, and fixes the second joint to an interior thereof; a seal member that is disposed on an inner wall of the second housing, and confines the refrigerant liquid leaked from a connection portion of the first joint and the second joint within a space formed when the first housing and the second housing are fitted to each other; and a water absorptive material that is disposed on an inner wall of the first housing, and absorbs the refrigerant liquid confined within the space.
 2. The liquid leakage prevention device according to claim 1, wherein a position at which the water absorptive material is located includes any one of all surfaces, a surface on which the refrigerant liquid is liable to be reserved, a lower surface, and lateral surfaces in the inner wall of the first housing.
 3. The liquid leakage prevention device according to claim 1, wherein a protrusion is provided on the water absorptive material, and a groove that fixes the protrusion to the inner wall of the first housing is provided.
 4. A liquid cooling system, comprising: a board on which an electronic component is mounted, which is inserted into a backplane or removed from the backplane; a heat receiving jacket that covers the electronic component, and internally circulates a refrigerant liquid to cool the electronic component at the time of inserting the board into the backplane; a pump that circulates the refrigerant liquid; a reserve tank that reserves the refrigerant liquid; a heat radiation unit that cools the refrigerant liquid; and a liquid leakage prevention device of a refrigerant liquid, wherein the liquid leakage prevention device, comprising: a first joint of a liquid connector which connects a pipe for allowing a refrigerant liquid to flow to a heat receiving jacket for cooling an electronic component mounted on a board; a second joint of the liquid connector which is fitted to the first joint; a first housing that fixes the first joint to an interior thereof; a second housing that is fitted to the first housing from an exterior, and fixes the second joint to an interior thereof; a seal member that is disposed on an inner wall of the second housing, and confines the refrigerant liquid leaked from a connection portion of the first joint and the second joint within a space formed when the first housing and the second housing are fitted to each other; and a water absorptive material that is disposed on an inner wall of the first housing, and absorbs the refrigerant liquid confined within the space, wherein the board is connected to the backplane by an electric connector, and the heat receiving jacket on the substrate is connected to the backplane by the liquid connector having the first and second joints, and the pump circulates the refrigerant liquid in a path including the reserve tank, the liquid connector having the first and second joints, the heat receiving jacket, and the heat radiation unit, to cool the refrigerant liquid.
 5. The liquid cooling system according to claim 4, wherein the water absorptive material is a water swellable water stop material, the liquid cooling system further comprises: a pressure sensor that is disposed on the inner wall of the first housing; and a detection unit that detects the liquid leakage by the water absorptive material and the pressure sensor.
 6. The liquid cooling system according to claim 4, wherein the water absorptive material is a water swellable water stop material, the liquid cooling system further comprises: a switch that is disposed on the inner wall of the first housing; and a detection unit that detects the liquid leakage by the water absorptive material and the switch.
 7. The liquid cooling system according to claim 4, further comprising: a water leakage sensor that is disposed on the inner wall of the first housing; and a detection unit that detects the liquid leakage by the water leakage sensor.
 8. The liquid cooling system according to claim 4, further comprising: a first flow rate sensor that is disposed on an inflow side of the reserve tank; a second flow rate sensor that is disposed on an outflow side of the reserve tank; and a detection unit that detects the liquid leakage by monitoring a difference between the first flow rate sensor and the second flow rate sensor.
 9. The liquid cooling system according to claim 5, wherein the detection unit stops the operation of the pump when detecting the liquid leakage. 